Well, if it was about "ils/elles sont" vs "ce sont" it sort of was there, in that it explicitly used "sont" (conjugation of être), but perhaps not explicitly stated. I can't say for sure since there's more than one long discussion on the subject and I don't know which you're referring to! :)
No, because in that sentence "elles sont" would have to change to "ce sont". "Il/Elle est + modified noun" changes to "c'est + modified noun". "Il/Elle est + adjective" stays "il/elle est + adjective". This only occurs with the verb "être" (to be), with all other verbs you use the pronoun.
"elles ont des robes" means that "they", a group composed entirely of females or grammatically feminine things/animals, have (some) dresses. "ils ont des robes" means that "they", a group with at least one man or grammatically masculine thing/animal, have (some) dresses. Both translate to "They have (some) dresses" in English, because English doesn't have the distinction between feminine and masculine that French does.
"ce ont des robes" is grammatically incorrect and doesn't mean anything.
Well, as was stated earlier, des is a french word that dosnt translate exacly to english. Its just a form of french grammer. It says that they have more than one dress without saying how many they have. A very vauge translation of the word would be "some" idk if any of that made since but i hope it helped ;)
I would personally ONLY CONSIDER inserting "some" into the English translation when the innately plural French partitive articles (articles partitif) of "du" [masculine], "de la" [feminine], "de l'" [for nouns/objects beginning with a French vowel or silent "h" or "y", of either gender] are used; and they are only used before UNCOUNTABLE NOUNS OR OBJECTS such as water, wine, bread or cake etc (especially when no unit of measure is given to them such as a bottle(s), a glass(es), a loaf/loaves).
Countable nouns such as dresses use the indefinte articles of "un", "une" for singular masculine or feminine nouns/objects respectively and "des" for plural numbers of nouns/objects of either gender. Note that in the latter use of "des", inserting "some" into the English translation is optional or even odd/misleading!
"Il/Elle est + modified noun" changes to "c'est + modified noun". "Il/Elle est + adjective" stays "il/elle est + adjective". This only occurs with the verb "être" (to be), with all other verbs you use the pronoun.
I think you missed the point. It's not that "they" can't mean women. It's that we're not told what "they" are, so we don't try to guess what "elles" are and translate to a noun, we translate to the equivalent English pronoun, "they". You only translate to "the women", "the girls", etc. if the French sentences has "les femmes", "les filles"...